Articulated surgical instrument for performing minimally invasive surgery with enhanced dexterity and sensitivity

ABSTRACT

An articulated surgical instrument for enhancing the performance of minimally invasive surgical procedures. The instrument has a high degree of dexterity, low friction, low inertia and good force reflection. A unique cable and pulley drive system operates to reduce friction and enhance force reflection. A unique wrist mechanism operates to enhance surgical dexterity compared to standard laparoscopic instruments. The system is optimized to reduce the number of actuators required and thus produce a fully functional articulated surgical instrument of minimum size.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation of, and claims the benefit ofpriority from, co-pending U.S. patent application Ser. No. 09/340,946,filed Jun. 28, 1999, which is a continuation of U.S. patent applicationSer. No. 09/030,661, filed Feb. 25, 1998 (now U.S. Pat. No. 5,976,122),which is a continuation of U.S. patent application Ser. No. 08/857,776,filed May 16, 1997 (now U.S. Pat. No. 5,792,135), which claims priorityto U.S. Provisional Application No. 60/017,981, filed May 20, 1996, thefull disclosures of which are incorporated herein by reference.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT NOT APPLICABLE REFERENCE TO A “SEQUENCELISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON ACOMPACT DISK. NOT APPLICABLE BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to methods and apparatus forenhancing the performance of minimally invasive surgery. This inventionrelates particularly to surgical instruments that augment a surgeon'sability to perform minimally invasive surgical procedures. Thisinvention relates more particularly to a novel articulated surgicalinstrument for minimally invasive surgery which provides a high degreeof dexterity, low friction, low inertia and good force reflection.

[0004] 2. Background of the Invention

[0005] Minimally invasive medical techniques are aimed at reducing theamount of extraneous tissue which must be damaged during diagnostic orsurgical procedures, thereby reducing patient recovery time, discomfort,and deleterious side effects. Approximately 21,000,000 surgeries are nowperformed each year in the United States. It is estimated that 8,000,000of these surgeries can potentially be performed in a minimally invasivemanner. However, only about 1,000,000 surgeries currently use thesetechniques due to limitations in minimally invasive surgical instrumentsand techniques and the additional surgical training required to masterthem.

[0006] Advances in minimally invasive surgical technology could have adramatic impact. The average length of a hospital stay for a standardsurgery is 8 days, while the average length for the equivalent minimallyinvasive surgery is 4 days. Thus, the complete adoption of minimallyinvasive techniques could save 28,000,000 hospital days, and billions ofdollars annually in hospital residency costs alone. Patient recoverytimes, patient discomfort, surgical side effects, and time away fromwork are also reduced with minimally invasive surgery.

[0007] The most common form of minimally invasive surgery is endoscopy.Probably the most common form of endoscopy is laparoscopy which isminimally-invasive inspection and surgery inside the abdominal cavity.In standard laparoscopic surgery, a patient's abdomen is insufflatedwith gas, and cannula sleeves are passed through small (approximately{fraction (1/2)} inch) incisions to provide entry ports for laparoscopicsurgical instruments.

[0008] The laparoscopic surgical instruments generally include alaparoscope for viewing the surgical field, and working tools such asclamps, graspers, scissors, staplers, and needle holders. The workingtools are similar to those used in conventional (open) surgery, exceptthat the working end of each tool is separated from its handle by anapproximately 12-inch long extension tube.

[0009] To perform surgical procedures, the surgeon passes instrumentsthrough the cannula and manipulates them inside the abdomen by slidingthem in and out through the cannula, rotating them in the cannula,levering (i.e., pivoting) the instruments in the abdominal wall andactuating end effectors on the distal end of the instruments. Theinstruments pivot around centers of rotation approximately defined bythe incisions in the muscles of the abdominal wall. The surgeon monitorsthe procedure by means of a television monitor which displays theabdominal worksite image provided by the laparoscopic camera.

[0010] Similar endoscopic techniques are employed in arthroscopy,retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy,sinoscopy, hysteroscopy and urethroscopy. The common feature of all ofthese minimally invasive surgical techniques is that they visualize aworksite within the human body and pass specially designed surgicalinstruments through natural orifices or small incisions to the worksiteto manipulate human tissues and organs thus avoiding the collateraltrauma caused to surrounding tissues which would result from creatingopen surgical access.

[0011] There are many disadvantages of current minimally invasivesurgical technology. For example, existing MIS instruments deny thesurgeon the flexibility of tool placement found in open surgery. Mostlaparoscopic tools have rigid shafts and are constrained to approach theworksite from the direction of the small incision. Additionally, thelength and construction of many endoscopic instruments reduces thesurgeon's ability to feel forces exerted by tissues and organs on theend effector of the tool. The lack of dexterity and sensitivity providedby endoscopic tools is a major impediment to the expansion of minimallyinvasive surgery.

[0012] Telesurgery systems for use in surgery are being developed toincrease a surgeon's dexterity as well as to allow a surgeon to operateon a patient from a remote location. Telesurgery is a general term forsurgical systems where the surgeon uses some form of servomechanism tomanipulate the surgical instruments movements rather than directlyholding and moving the tools. In a system for telesurgery, the surgeonis provided with an image of the patient's body at the remote location.While viewing the threedimensional image, the surgeon performs thesurgical procedures on the patient by manipulating a master device whichcontrols the motion of a servomechanism-actuated instrument. Thesurgeon's hands and the master device are positioned relative to theimage of the operation site in the same orientation as the instrument ispositioned relative to the act. During the operation, the instrumentprovides mechanical actuation and control of a variety of surgicalinstruments, such as tissue graspers, needle drivers, etc., that eachperform various functions for the surgeon, i.e., holding or driving aneedle, grasping a blood vessel or dissecting tissue.

[0013] Such telesurgery systems have been proposed for both open andendoscopic procedures. An overview of the state of the art with respectto telesurgery technology can be found in “Computer Integrated Surgery:Technology And Clinical Applications” (MIT Press, 1996). Moreover, priorsystems for telesurgery are described in U.S. Pat. Nos., 5,417,210,5,402,801, 5,397,323, 5,445,166, 5,279,309, 5,299,288.

[0014] However methods of performing telesurgery using telemanipulatorsstill require the development of dexterous surgical instruments capableof transmitting position, force, and tactile sensations from thesurgical instrument back to the surgeon's hands as he/she operates thetelesurgery system such that the system the surgeon has the same feelingas if manipulating the surgical instruments directly by hand. A system'sability to provide force reflection is limited by factors such asfriction within the mechanisms, gravity, the inertia of the surgicalinstrument and forces exerted on the instrument at the surgicalincision.

[0015] What is needed, therefore, is a surgical instrument thatincreases the dexterity with which a surgeon can perform minimallyinvasive surgical procedures.

[0016] It would also be desirable to provide a dexterous surgicalapparatus having a wrist with two degrees-of-freedom.

[0017] It would further be desirable to provide a wrist mechanism thathas low friction in order to provide the surgeon with sensitive feedbackof forces exerted on the surgical instrument.

[0018] It would still further be desirable to provide a surgicalinstrument having a wrist mechanism for minimally invasive surgery whichis suitable for operation in a telemanipulator mechanism.

BRIEF SUMMARY OF THE INVENTION

[0019] Accordingly, it is an object of this invention to provide asurgical instrument that increases the dexterity with which a surgeoncan perform minimally invasive surgical procedures.

[0020] It is also an object of this invention to provide a dexteroussurgical apparatus having a wrist with two degrees-of-freedom.

[0021] It is a further object of this invention to provide a wristmechanism that has low friction in order to provide the surgeon withsensitive feedback of forces exerted on the surgical instrument.

[0022] It is a still further object of this invention to provide asurgical instrument having a wrist mechanism for minimally invasivesurgery which is suitable for operation in a telemanipulator mechanism.

[0023] In accordance with the above objects of the invention applicantsdescribe a compact articulated surgical instrument suitable forendoscopic surgery. The instrument has two opposed pivoting jaws and apivoting wrist member. The instrument is capable of providing forcereflection with high sensitivity. The instrument is adapted to becoupled via a servomechanism to a master control operated by a surgeon.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the drawings in which likereference characters refer to the same parts throughout the differentviews. The drawings are not necessarily to scale, emphasis instead beingplaced upon illustrating the principles of the invention.

[0025]FIG. 1 is a schematic drawing of a servomechanical surgery systemincluding a force-reflecting surgical instrument mounted to apositioning mechanism.

[0026]FIG. 2 is a schematic drawing of a positioning mechanism inforward and rearward positions with the surgical instrument insertedinto a patient.

[0027]FIG. 3 is a perspective view of a force-reflecting surgicalinstrument.

[0028]FIG. 4 is a schematic view of the cable drive actuation of therotary motion of the force-reflecting surgical instrument.

[0029]FIG. 5 is a perspective view of the distal end of theforce-reflecting surgical instrument.

[0030]FIG. 6 is a simplified schematic drawing of the force-reflectingsurgical instrument showing the relationship of the cables and pulleys.

[0031]FIG. 7a is a perspective view of a cable wrapped around the driveshaft of a drive motor.

[0032]FIG. 7b is a schematic drawing showing another preferred methodfor driving the cables in the present invention.

[0033]FIG. 8 is a top view of the wrist member of another preferredforce-reflecting surgical instrument.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The surgical instrument in the first embodiment includes anelongate support member having a proximal portion and a distal portionlying along a longitudinal axis. A distal wrist member is rotatablycoupled to the distal portion of the support member by a wrist joint.First and second opposed work members are mounted to respective firstand second driven capstans. The first and second driven capstans arerotatably mounted to the wrist member by respective first and secondcapstan joints which preferably have a common axis. First, second, thirdand fourth intermediate idler pulleys are rotatably mounted to the wristmember about the wrist joint. A cable drive system including first,second, third and fourth cables is provided. Each intermediate idlerpulley is engaged by one cable and each driven capstan is drivinglyengaged by two cables. The cable drive system is capable of pivoting thewrist member about the wrist joint and pivoting the work membersindependently of each other about the capstan joints.

[0035] In preferred embodiments, a linear bearing is mounted in slidingengagement with the support member for allowing the distal portion ofthe support member to be reciprocated along the longitudinal axisrelative to the proximal portion of the support member. In suchembodiments the cable drive system is capable of translating the supportmember along the longitudinal axis. In preferred embodiments, thesupport member may also include a rotary joint separating the proximaland distal portions of the support member for allowing rotation of thedistal portion relative to the proximal portion about the longitudinalaxis. In such embodiments the first through fourth cables are capable oftwisting about the longitudinal axis during rotation of the distalportion and the cable drive system comprises a fifth cable coupled tothe rotary joint for rotating the distal portion about the longitudinalaxis.

[0036] The present invention also provides a novel system for tensioningthe first, second, third and fourth cables. A first proximal idlerpulley rotatably engages and tensions the first and second cables. Asecond proximal idler pulley rotatably engages and tensions the thirdand fourth cables. Fifth and sixth cables are connected to the first andsecond proximal idler pulleys for tensioning the first and secondproximal idler pulleys. A third more proximal idler pulley is rotatablymounted to a support member for rotatably engaging and tensioning thefifth and sixth cables.

[0037] The surgical instrument further includes a plurality ofactuators, each for driving one of the cables of the cable drive system.The instrument preferably comprises one actuator for eachdegree-of-freedom of the instrument. The actuators are preferablyservomotors which are positioned between the intermediate idler pulleysand the proximal idler pulleys. The servomotors are preferably directlycoupled to the cables by means of a drive capstan mounted on the driveshaft of the servomotor.

[0038] The surgical instrument is adapted to be a slave device which iscontrolled by a master device and a controller. Movements of theinstrument and the master device as well as forces exerted thereon maybe scaled between the instrument and the master device. A positioningmechanism having two degrees-of-freedom may be mounted to the instrumentfor positioning the instrument over a work site. The positioningmechanism may provide the instrument with redundant degrees-of-freedomfor positioning the endpoint. The combination of a positioning mechanismwith the applicants articulated surgical instrument is adapted to enablea surgeon operating the master device to feel forces that areexperienced by the instrument during positioning and use of theinstrument with greater sensitivity than with prior systems.

[0039] Details about the preferred attributes of the surgical system arealso described in applicants' copending applications titled“Force-Reflecting Surgical Instrument And Positioning Mechanism ForPerforming Minimally Invasive Surgery With Enhanced Dexterity AndSensitivity” and “Wrist Mechanism For Surgical Instrument For PerformingMinimally Invasive Surgery With Enhanced Dexterity And Sensitivity”filed on even date herewith. The disclosures of these applications areincorporated herein by reference.

[0040] Referring to FIG. 1, telesurgery system 10 allows a surgeon atone location to perform surgery on a patient at another location. Thesurgeon may be in the same operating room as the patient or many milesaway. Telesurgery system 10 includes a force-reflecting surgicalinstrument 12 which is mounted by a bracket 36 to a positioningmechanism 14. Instrument 12 and positioning mechanism 14 are controlledby a computer 11 and a master device 150 which is manipulated by asurgeon at a remote location. Instrument 12 and positioning mechanism 14are driven by drive motors M1, M2, M3, M4, M5, M6 and M7 (FIGS. 3, 4, 6and 7 a-b) in conjunction with a series of cables and pulleys.

[0041] Instrument 12 has low friction, low inertia and high bandwidthbut a small range of motion. Positioning mechanism 14 has a large rangeof motion but typically has a higher inertia and a lower bandwidth thanthe instrument. The combination of instrument 12 and positioningmechanism 14 in a macro/micro actuation scheme results in a system withincreased dynamic range compared to either of its individual components.Positioning mechanism 14 provides telesurgery system 10 with redundantdegrees-of-freedom and helps positions instrument 12 at a surgicalworksite so that instrument 12 is generally in the proper location forperforming the necessary surgery. Thus, by mounting instrument 12 onpositioning mechanism 14, telesurgery system 10 is provided with highquality force control through the use of instrument 12 while at the sametime having a large range of motion due to positioning mechanism 14.Instrument 12 is mounted on positioning mechanism by means of mountingbracket 36. Preferably, the Instrument 12 is releasably attached topositioning mechanism 14 using any suitable releasable attachment meanssuch as screws, bolts, clamps.

[0042] Instrument 12 has a proximal portion 28 a which is rotatablycoupled to a distal portion 28 b by a rotary joint 26. Proximal portion28 a is slidably coupled to a sliding bracket 96 which forms a slidingjoint 30. Sliding bracket 96 is fixed to bracket 36. Bracket 36 is amounting bracket which releasably connects instrument 12 to positioningmechanism 14. Distal portion 28 b of instrument 12 includes a wristmember which is rotatably coupled to a tubular support member 24 by awrist joint 16. Two opposed work members 20 a and 20 b are fixed torespective driven capstans 18 a and 18 b which are rotatably coupled towrist member 22 about capstan joints 19 a and 19 b. The work members 20a and 20 b can be the operative end of standard surgical instrumentssuch as scissors, retractors, needle drivers and electrocauteryinstruments.

[0043] Instrument 12 has five degrees-of-freedom with sliding joint 30providing linear motion along longitudinal axis C-C, rotary joint 26providing rotational motion about axis C-C, wrist joint 16 providingrotational motion about axis B-B and capstan joints 19 a and 19 bproviding rotational motion about axis A-A for work members 20 a and 20b. Instrument 12 provides master device 150 with four degrees of forcereflection so that the surgeon can have tactile feedback of surgicalprocedures. These degrees of force reflection include x, y and z forcesexerted on the work members 20 a and 20 b, as well as the holding forcebetween work members 20 a and 20 b. However, force reflection can beprovided on more or fewer motion axes as required in any particularembodiment.

[0044] Positioning mechanism 14 is a two degree-of-freedom linkage whichis preferably a four bar linkage which rotates about an axis E-E.Positioning mechanism 14 has a series of rigid members 36, 40, 42, 60and 62 which are joined together by joints 34, 38, 48, 50, 52, 54, 56.Positioning mechanism 14 also includes a base 68 having ears 58 whichengage shafts 64 and 66 to form a joint 57 for pivoting about axis E-E.Joint 56 allows link 62 to rotate about axis D-D which is orthogonal toaxis E-E. The four bar linkage of rigid members 36, 40, 42, 60 and 62transmits this rotation to instrument 12 via bracket 36 causinginstrument 12 to rotate about axis E-E and axis D′-D′(axis D′-D′isparallel to axis D-D and intersects axis E-E orthogonally). Thus thefour bar linkage operates to move point P_(s) of instrument 12 about thesurface of a sphere having its center at a remote center 111. Although afour bar linkage has been shown, the articulated surgical instrument ofthe present invention can be supported by any suitable positioningmechanism. To be suitable for minimally invasive surgery the positioningmechanism must pivot the surgical instrument about axes that intersectat the orifice through which the instrument is inserted into thepatient.

[0045] Haptic master device 150 suitable to control instrument 12 is aseven degree-of-freedom input device. During use the master 150 is fixedin place to a console or cart or similar stationary support such thatthe mount provides a fixed reference point. During use, the surgeonmanipulates the position and orientation of the master mechanismrelative to its stationary support. Linkages, motors and encoders of themaster detect the surgeon's movements and transmit them to the computer.The motors of the master preferably also provide force feedback to thesurgeon. This controls motions of instrument 12 and positioningmechanism 14 and thus controls the position of the distal end ofinstrument 12 relative to the surgical site.

[0046] One apparatus suitable for use as a master in the presentlydescribed system is described in U.S. Pat. No. 5,587,937, titled ForceReflecting Haptic Interface the contents of which are incorporated byreference herein. Another suitable master device is described in U.S.Pat. No. 5,576,727, titled Electromechanical Human-Computer InterfaceWith Force-Feedback the contents of which are incorporated by referenceherein. The haptic master apparatus disclosed in the above referenceswould require the addition of a further powered degree-of-freedom toprovide force reflection from gripping the work members. For example,finger grippers may be attached to a motor and encoder on a separatemechanism for operation by the other hand of the surgeon. Alternatively,finger grippers may be attached to a motor and encoder on the samedevice for operation by the surgeon.

[0047] When employing telesurgery system 10 for laparoscopic surgery,positioning mechanism 14 is mounted to a manually-operated setup joint(not shown). After the setup joint has been used to position the tooland lock the tool in place, the surgeon then manipulates master device150 to move instrument 12 through a cannula 113 inserted through smallincision 112 in the abdominal wall 110 of the patient. In response tomanipulation of master device 150, the distal portion 28 b of theinstrument 12 is translated downwardly relative to positioning mechanism14 along sliding joint 30 for insertion through cannula 113 andabdominal wall 110.

[0048] Once within the abdomen, the distal portion 28 b of instrument 12is further positioned over the desired surgical site. FIG. 2 depictsmotion of mechanism 14 pivoted about axis D-D in forward and rearwardpositions for making large position movements. Positioning mechanism 14pivots about axes D-D and E-E to perform large movements of telesurgerysystem 10 while precise movements are made by the joints of instrument12. Point 111 on instrument 12 is a remote point of rotation frompositioning mechanism 14 which coincides with entry wound 112. Whenpositioning mechanism 14 is pivoted about axes D and E, instrument 12pivots about point 111. Note that point 111 adjacent incision 112remains stationary as the instrument 12 is pivoted within the patient.As a result, incision 112 only needs to be large enough to acceptinstrument 12.

[0049] As positioning mechanism 14 pivots, if wrist member 22 or workmembers 20 a/20 b engage tissue causing rotation about joints 16 or 19a/19 b, instrument 12 will reorient itself so that instrument 12 ismaintained relative to positioning mechanism 14 in the middle of itsworkspace. If necessary, positioning mechanism 14 can slow down asinstrument 12 is reorienting itself.

[0050] Once instrument 12 is in the proper position, by furthermanipulating master device 150, the surgeon can perform the necessarysurgical procedures on the patient with instrument 12. Forcesexperienced by instrument 12 are reflected back to the surgeon by masterdevice 150. The reflected forces may be scaled up in order to allow thesurgeon to better “feel” the surgical procedures. As a result, thesurgeon can feel instrument 12 engaging types of tissue that do notprovide much resistance. In addition, movements of master device 150relative to instrument 12 may be scaled down so that the precision anddexterity of instrument 12 can be increased.

[0051] Positioning mechanism 14, because it is optimized to have a largerange of motion, is likely to have higher inertia, higher friction andlower resolution than instrument 12. Moreover, friction forces incannula 113 and disturbance forces at incision 112 may be applied to thepositioning mechanism. However, in applicants' preferred embodiment,primarily the surgical instrument detects forces for force reflection.Therefore, the higher inertia and friction of the positioning mechanismand the extraneous forces acting on it are excluded from the forcereflection system. Thus, the quality of the force reflection between thetip of the instrument 12 and the master device is greatly improved.

[0052] Referring to FIGS. 3, 4 and 5, instrument 12 is now described ingreater detail. Tubular support member 24 of distal portion lies alongaxis C-C and houses a series of cables C1, C2, C3 and C4 which travelthe length of tubular support member 24. Cables C1, C2, C3 and C4control the rotation of joints 19 a, 19 b and 16 for controlling theoperation of work members 20 a and 20 b and the orientation of wristmember 22. Wrist member 22 includes two opposed distal ears 21 a and 21b forming a clevis for supporting driven capstans 18 a and 18 b atrespective capstan joints 19 a and 19 b which lie along axis A-A. Wristmember 22 also includes two opposed proximal ears 23 a and 23 b forminga clevis for supporting intermediate idler pulleys 70 and 72 which liealong axis B-B between ear 23 a and tongue 24 a at wrist joint 16.Intermediate idler pulleys 74 and 76 are supported between ear 23 b andtongue 24 a. Cables C1, C2, C3 and C4 engage driven capstans 18 a/18 bas well as intermediate idler pulleys 70, 72, 74 and 76 as describedlater in greater detail.

[0053] Work members 20 a and 20 b may be removably fixed to respectivedriven capstans 18 a and 18 b. Although work members 20 a and 20 b aredepicted in the figures as being grippers, work members 20 a and 20 bcan be replaced with other types of work members such as scissors,cutters, graspers, forceps or needle holders for stitching sutures.Typically, the work members are fixed to driven capstans 18 a and 18 bby a screw, clip or other suitable fastener. However, the work membersmay also be permanently affixed to the driven capstans by soldering orwelding, or the like, or may be formed in one piece with the drivencapstans.

[0054] Work members 20 a and 20 b together comprise one form of surgicalend effector. Other surgical end effectors may be used in the surgicalinstrument of the present invention. End effectors simply may comprisestandard surgical or endoscopic instruments with their handles removedincluding, for example, retractors, electrocautery instruments,microforceps, microneedle holders, dissecting scissors, blades,irrigators, and sutures. The end effectors will typically comprise oneor two work members.

[0055] Proximal portion 28 a of instrument 12 includes support brackets98 and 102 which are connected together by a support rod 100 as well astwo guide rails 104 and 106. A rotary bearing 91 forming rotary joint 26is housed within support bracket 98 for supporting tubular supportmember 24. Sliding bracket 96 is slidably mounted to guide rails 104 and106 along linear bearings. As shown in FIG. 1, sliding bracket 96 isconnected by bracket 36 to positioning mechanism 14. Sliding bracket 96preferably has about 8 inches of travel for surgical applications.

[0056] Drive motors M1, M2, M3, M4 and M5 are mounted to sliding bracket96 and drive respective cables C1, C2, C3 and C4 and C5. Sliding bracket96 supports each of the drive motors. During operation sliding bracket96 is connected to positioning mechanism 14 by mounting bracket 36. Wheninstrument 12 is mounted on positioning mechanism 14, the drive motorsoperate to move distal portion 28 b relative to sliding bracket 96.Sliding bracket 96 thus forms the support bracket of the surgicalinstrument. Each drive motor M1, M2, M3, M4 and M5 includes a respectiveencoder E1, E2, E3, E4 and E5 for providing computer 11 with therotational position of their respective drive shafts.

[0057] As shown in FIG. 4, drive motor M5 has a drive shaft capstan 93which engages a cable drive loop consisting of Cable C5. The cablepasses around rear tensioning pulley 83. The cable passes around idlerpulleys 84 and 85 and around drive capstan 90 which forms the proximalend of tubular support member 24. Thus rotation of actuation of motor M5can be used to rotate tubular support member 24 and the end effector itsupports.

[0058] Referring to FIG. 6, the cable drive system of instrument 12 isnow described in greater detail. Work members 20 a and 20 b, wristmember 22 and the translation of instrument 12 along longitudinal axisC-C are driven by cables C1, C2, C3 and C4 which are arranged in an N+1actuation scheme. The N+1 actuation scheme allows the actuation of athree degree-of-freedom wrist using four cables. Four cables is thetheoretical minimum possible number of tension elements required todrive three degrees-of-freedom and thus allows the instrument to be ofminimum size and weight. Alternative actuation schemes using more cablesmay be desirable in situations where the forces required for actuationof different motions differ greatly in magnitude. The disadvantage ofusing more cables is an increase in weight, complexity and minimum size.

[0059] In FIG. 6, the rotational motion of joint 26 about axis C-C isomitted in order to more easily show cables C1-C4. Such rotation resultsonly in twisting of the cables C1-C4 between motors M1-M4 and pulleys70, 72, 74 and 76. The cables are however arranged in tubular supportmember 24 such that this twisting does not significantly change thelength of the cable path. Care should however be taken to preventover-rotation of the instrument which would cause the cables to twistinto contact with each other and create friction between the cables.

[0060] As shown in FIG. 6, cables C1 and C2 form two sides of acontinuous cable loop 44. Cable C1 of loop 44 engages a proximal idlerpulley 80, the drive shaft of motor M1, intermediate idler pulley 70 anddriven capstan 18 a. Cable loop 44 returns from driven capstan 18 a ascable C2 and engages intermediate idler pulley 76, the S drive shaft ofmotor M2 and proximal idler pulley 80.

[0061] As shown in FIG. 6. cables C3 and C4 form two sides of acontinuous loop of cable 46. Cable C3 of cable loop 46 engages proximalidler pulley 78, the drive shaft of motor M3. intermediate idler pulley72 and driven capstan 18 b. Cable loop 46 returns from driven capstan 18b as cable C4 and engages intermediate idler pulley 74, the drive shaftof motor M4 and proximal idler pulley 78.

[0062] As shown in FIG. 6, proximal idler pulleys 78 and 80 aretensioned by cables C7 and C6 which are fixed to the center of proximalidler pulleys 78 and 80. Cables C7 and C6 form two sides of a singlecable 45 which engages proximal idler pulley 82 which is rotatablymounted to support bracket 102 by shaft 82 a. Shaft 82 a is preferablymovably mounted to support bracket 102 by a mechanism such as a leadscrew. The lead screw may then be adjusted to appropriately tensioncables C7 and C6. The tension is also applied via idler pulleys 78 and80 to cables C1, C2, C3 and C4. A similar lead screw tensioning schemecan be used to tension cable C5 by longitudinal movement of idler pulley83. It may be required for idler pulleys 82 and 83 to be mounted onseparately adjustable shafts for these purpose instead of single shaft82 a illustrated in FIG. 3.

[0063] Driven capstans 18 a and 18 b may have different diameters inorder to allow cables C1 through C4 to suitably engage their respectiveintermediate idler pulleys. Cables C1 and C2 engage the outerintermediate idler pulleys 70 and 76 while cables C3 and C4 engage theinner intermediate idler pulleys 72 and 74. Proximal idler pulleys 78and 80 are sized such that pulley 80 is larger than pulley 78 to keepthe cables straight.

[0064] Drive motors M1, M2, M3 and M4 control rotation of wrist member22 about axis B-B, translation of instrument 12 longitudinally alongaxis C-C and rotation of work members 22 a and 22 b independent of eachother about axis A-A by driving cables C1, C2, C3 C3/C4 driven by drivemotors M3 and M4 in order to rotate wrist member 22 about axis B-B.Drive motor M1 drives cable C1 in opposition to cable C2 driven by drivemotor M2 to rotate capstan 18 a and attached work member 20 a about axisA-A. In addition, drive motor M3 drives cable C3 in opposition to cableC4 driven by drive motor M4 to rotate capstan 18 b and attached workmember 20 b about axis A-A. All four drive motors M1, M2, M3 and M4drive cables C1, C2, C3 and C4 simultaneously to translate instrument 12along longitudinal axis C-C.

[0065] Locating drive motors M1, M2, M3, M4 and M5 on sliding bracket 96makes the distal portion 28 b of instrument 12 have a small moving masssince the motors themselves remain stationary during actuation of theinstrument. Although the motors are moved by positioning mechanism 14,the weight and inertia of the motors do not affect force reflection.This is because, as stated above, in the preferred embodiment, only theinstrument is used to reflect forces to the master. In addition,employing cables instead of gears to control instrument 12 minimizes theamount of friction and backlash within instrument 12. The combination ofsmall moving masses and low friction enables instrument 12 to provideforce reflection to master device 150 with high sensitivity.

[0066] Certain possible changes to the configuration of pulleys, cablesand motors described above will be apparent to those of skill in theart. Although cables C1/C2, C3/C4, C5 and C7/C6 have been depicted to besides of the same cables, cables C1-C7 alternatively can each beindividual cables which are fixed to driven capstans 18 a and 18 b, andproximal idler pulleys 78, 80 and 82. Moreover, although drive motorsM1, M2, M3 and M4 have been depicted to drive cables C1, C2, C3 and C4respectively, alternatively, some drive motors can be relocated fromcables C1-C4 onto cables C7 and C6 for driving cables C7 and C6. Thechoice of the particular drive scheme employed in a particularembodiment will depend on the constraints of the forces required to beexerted by the instrument and the need to reduce the inertia andfriction of the parts of the instrument that move during its actuation.

[0067] The surgical instrument of the present invention has beenillustrated as using drive motors M1, M2, M3, M4 and MS. This drivemotors may be standard servo motors having position encoders as shown inFIG. 3. However, other actuators may be used, such as hydraulicactuators and piezoelectric motors. To be used as an actuator in thepresent surgical instrument a drive mechanism should be able to providevariable and controllable force and position control.

[0068] Cables C1, C2, C3, C4, C7, C8 and C9 are driven by being wrappedabout the drive shaft of their respective drive motors M1, M2, M3, M4,M5, M6 and M7. This cable drive method and an alternative cable drivemethod are illustrated in more detail in FIGS. 7a and 7 b. For example,in FIG. 7a, cable C4 of cable loop 46 is wrapped around the drive shaftof motor M4. Cable C4 is preferably wrapped two times around the driveshaft to provide enough friction between the cable C4 and the driveshaft to prevent slippage. In order to further prevent slippage thecable may be fixed to the drive shaft at one point by soldering, weldingor mechanical fixing means. However, in such an embodiment the range ofmotion of the cable is limited by the length of cable wrapped around thedrive shaft or capstan thus several turns of cable are usually required.

[0069]FIG. 7b depicts another preferred method for driving cables. Forexample, motor M4 includes a drive wheel 43 a and a idler wheel 43 b forfrictionally driving an elongate member 47 therebetween. Cable C4consists of two halves, 46 a and 46 b which are fixed to opposite endsof member 47.

[0070]FIG. 8 depicts the distal end and wrist member 116 of anotherpreferred instrument 117. Instrument 117 differs from instrument 12 inthat instrument 117 includes eight intermediate idler pulleys instead offour. Instrument 117 includes intermediate idler pulleys 76, 74, 72 and70 at wrist joint 16 but also includes intermediate idler pulleys 76a,74 a, 72 a and 70 a which are positioned adjacent to idler pulleys 76,74, 72 and 70 on tongue 24 a along shaft 118. Cables C1, C2, C3 and C4do not make a complete wrap around each intermediate idler pulley butinstead contacts a variable amount of the surface of each pulley varyingin a range between 0° and 180° over the range of motion of the wristabout axis 16. This prevents the cables from crossing each other andrubbing together which prevents friction and noise.

[0071] Although the present invention has been described for performinglaparoscopic surgery, it may also be used for other forms of endoscopicsurgery as well as open surgery. The present manipulator could also beemployed for any suitable remote controlled application requiring adexterous manipulator with high quality force feedback. Moreover, whilethis invention has been particularly shown and described with referencesto preferred embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims.

What is claimed is:
 1. An articulated instrument for minimally invasivesurgery, comprising: an elongate support member having a proximalportion and a distal end with a longitudinal axis therebetween; apivotal wrist member disposed at the distal end of the elongate supportmember; and a surgical end effector coupled to the wrist member, the endeffector including at least one end effector work member, the workmember being removably fixed to the wrist member; said articulatedinstrument having a size and shape suitable for distal insertion into aninternal surgical site through an aperture.
 2. The articulatedinstrument of claim 1, further comprising at least one wrist driveelement coupled to the wrist member and adapted for coupling to at leastone actuator for pivoting the wrist member about a wrist joint.
 3. Thearticulated instrument of claim 2, wherein the wrist drive elementincludes a cable.
 4. The articulated instrument of claim 1, wherein theat least one end effector work member includes at least a pair of workmembers pivotally coupled to the wrist member, wherein at least one workmember can pivot relative to the other work member of the pair.
 5. Thearticulated instrument of claim 4, further comprising at least one endeffector drive element coupled to at least one end effector work memberand adapted for coupling to at least one actuator for pivoting the workmember relative to the wrist member.
 6. The articulated instrument ofclaim 5, wherein the end effector includes at least onepivotally-mounted capstan coupled to the end effector drive element, andthe at least one end effector work member is removably fixed to thecapstan.
 7. The articulated instrument of claim 6, wherein the endeffector drive element includes a cable.
 8. The articulated instrumentof claim 4, wherein one of said work members is pivotally connected tothe other work member, and both work members are pivotally connected tothe wrist member.
 9. The articulated instrument of claim 1, wherein theat least one end effector work member is removably fixed to the wristmember by at least one of a screw and a clip.
 10. The articulatedinstrument of claim 1, wherein the end effector comprises a gripper, ascissors, a cutter, a graspers, a forceps, a needle holder, a retractor,an electrocautery instrument, a microforceps, a microneedle holder, adissecting tool, a blade, or an irrigator, or a combination of these.11. The articulated instrument of claim 1, further comprising at leastone substitute member adapted to be removably fixed to the wrist memberto replace the at least one end effector work member.
 12. Thearticulated instrument of claim 11, wherein the substitute member is ofa different surgical type than the at least one end effector workmember.
 13. A minimally invasive surgical system including: an armhaving a proximal end portion adapted to be attached to a base so as topermit a distal end portion of the arm to move relative to the base; andan articulated surgical instrument mounted on the distal end of the arm,the instrument comprising: an elongate support member having a proximalportion and a distal end with a longitudinal axis therebetween; apivotal wrist member disposed at the distal end of the elongate supportmember; and at least one surgical end effector work member coupled tothe wrist member, the work member being removably fixed to the wristmember; said instrument having a size and shape suitable for distalinsertion into an internal surgical site through an aperture; and 14.The surgical system of claim 13, further comprising a drive systemincluding at least one wrist drive element coupled to the wrist memberand adapted for coupling to at least one actuator for pivoting the wristmember about a wrist joint.
 15. The surgical system of claim 14, whereinthe wrist drive element includes a cable.
 16. The surgical system ofclaim 13, wherein the at least one end effector work member includes atleast a pair of work members pivotally coupled to the wrist member,wherein at least one work member can pivot relative to the other workmember of the pair.
 17. The surgical system of claim 16, furthercomprising at least one end effector drive element coupled to at leastone end effector work member and adapted for coupling to at least oneactuator for pivoting the work member relative to the wrist member. 18.The surgical system of claim 17, wherein the end effector includes atleast one pivotally-mounted capstan coupled to the end effector driveelement, and the at least one end effector work member is removablyfixed to the capstan.
 19. The surgical system of claim 18, wherein theend effector drive element includes a cable.
 20. The surgical system ofclaim 16, wherein one of said work members is pivotally connected to theother work member, and both work members are pivotally connected to thewrist member.
 21. The surgical system of claim 13, wherein the at leastone end effector work member is removably fixed to the wrist member byat least one of a screw and a clip.
 22. The surgical system of claim 13,wherein the end effector comprises a gripper, a scissors, a cutter, agraspers, a forceps, a needle holder, a retractor, an electrocauteryinstrument, a microforceps, a microneedle holder, a dissecting tool, ablade or an irrigator, or a combination of these.
 23. The surgicalsystem of claim 13, further comprising at least one substitute memberadapted to be removably fixed to the wrist member to replace the atleast one end effector work member.
 24. The articulated instrument ofclaim 13, wherein the substitute member is of a different surgical typethan the at least one end effector work member.
 25. A method forminimally invasive surgery in a patient, comprising: (a) providing anarticulated surgical instrument including: an elongate support memberhaving a proximal portion and a distal end with a longitudinal axistherebetween; a pivotal wrist member disposed at the distal end of theelongate support member; and a surgical end effector coupled to thewrist member, the end effector including at least one end effector workmember, the work member being removably fixed to the wrist member; saidarticulated instrument having a size and shape suitable for distalinsertion into an internal surgical site through an aperture. (b)inserting a distal portion of the surgical instrument through anaperture in a patient's body to a location adjacent a surgical worksite,the distal portion including at least the wrist member and the endeffector; (c) performing a surgical treatment using the at least one endeffector work member; (d) removing the at least one end effector workmember from the wrist member; (e) providing a substitute member; (f)replacing the at least one end effector work member by removably fixingthe substitute member to the wrist member; and (g) performing a surgicaltreatment using the substitute member.
 26. The method of claim 25,further comprising the steps of: (h) prior to the removing step (d),retracting the distal portion from the aperture in the patient's body;and (i) following the replacing step (f), inserting the distal portionof the surgical instrument through an aperture in a patient's body to alocation adjacent a surgical worksite.
 27. The method of claim 25,further comprising the step of: (j) moving the wrist member to positionthe end effector for surgical treatment.
 28. The method of claim 27,wherein: the articulated instrument provided in step (a) furtherincludes at least one wrist drive element coupled to the wrist memberand adapted for coupling to at least one actuator for pivoting the wristmember about a wrist joint; and the moving step (j) includes actuatingthe wrist drive element to move the wrist member.
 29. The method ofclaim 28, wherein the wrist drive element includes a cable.
 30. Themethod of claim 25, wherein: the articulated instrument provided in step(a) further includes at least one end effector drive element coupled toat least one end effector work member and adapted for coupling to atleast one actuator for pivoting the work member relative to the wristmember; and at least one of the treatment performing steps (c) and (g)includes actuating the end effector drive element to pivot the at leastone end effector work member.
 31. The method of claim 30, wherein theend effector includes at least one pivotally-mounted capstan coupled tothe end effector drive element, and the at least one end effector workmember is removably fixed to the capstan.
 32. The method of claim 31,wherein the end effector drive element includes a cable.
 33. The methodof claim 25, wherein the at least one end effector work member of thearticulated instrument provided in step (a) is removably fixed to thewrist member by at least one of a screw and a clip.
 34. The method ofclaim 25, wherein the end effector of the articulated instrumentprovided in step (a) comprises a gripper, a scissors, a cutter, agraspers, a forceps, a needle holder, a retractor, an electrocauteryinstrument, a microforceps, a microneedle holder, a dissecting tool, ablade or an irrigator, or a combination of these.
 35. The method ofclaim 25, wherein the substitute member provided in step (e) is adifferent surgical instrument type than the at least one end effectorwork member provided in step (a).
 36. A minimally invasive surgicalsystem comprising: a base adapted to be fixed relative to a patient'sbody; an instrument positioning mechanism; an articulated surgicalinstrument assembly; and an instrument drive system; the instrumentpositioning mechanism including: a support linkage having a proximal endand a distal end, the proximal end being coupled the base and the distalend being coupled to the articulated surgical instrument assembly; apositioning drive system configured to move the distal end of thesupport linkage so as to move the articulated surgical instrumentassembly in a plurality of degrees of freedom relative to the base; thearticulated surgical instrument assembly including: a proximal portionand a distal portion, and an elongate support assembly having a proximalend and a distal end with a longitudinal axis therebetween; a pivotalwrist joint disposed adjacent the distal end of the elongate supportassembly, and a surgical end effector including a first end effectorelement coupled to the wrist joint by a first pivotal end effectorjoint; the proximal portion of the articulated surgical instrumentassembly being adapted to releasably couple to the distal end of theinstrument positioning mechanism; the distal portion of the articulatedsurgical instrument assembly having a size and shape suitable forinsertion through an aperture in the patient's body to extent to aninternal surgical site; and the instrument drive system including: aplurality of actuators disposed adjacent the distal end of thepositioning mechanism; a plurality of elongate drive elements extendinglongitudinally from the plurality of actuators to operatively couple toa corresponding plurality of pivotal joints adjacent the distal portionof the articulated surgical instrument assembly; the plurality ofpivotal joints including at least the pivotal wrist joint and the firstpivotal end effector joint; the instrument drive system being configuredto move the first end effector element in a plurality of degrees offreedom relative to the distal end of the positioning mechanism.
 37. Thesurgical system of claim 36, wherein the positioning mechanism furthercomprises a linear bearing coupling the articulated surgical instrumentassembly to the distal end of the support linkage, to permit axialtranslation of the articulated surgical instrument assembly relative tothe base.
 38. The surgical system of claim 36, wherein the cableelements are configured to hold the plurality of pivotal joints at fixedangles when the actuators do not move the cable elements and thearticulated surgical instrument assembly is translated axially.
 39. Thesurgical system of claim 36, wherein the elongate elements comprisecable elements including at least one portion of cable.
 40. The surgicalsystem of claim 39, wherein the cable elements are configured to twistwithin the elongate support assembly so that the distal portion of thearticulated surgical instrument assembly can rotate about the axisrelative to the positioning mechanism and the actuators.
 41. Thesurgical system of claim 39, wherein at least one of the plurality ofcable element comprises a continuous loop.
 42. The surgical system ofclaim 39, wherein the positioning mechanism is configured to cause thearticulated surgical instrument assembly to pivot about at least a firstaxis relative to the base.
 43. The surgical system of claim 36, whereinthe instrument drive system includes a rotational connection arranged topermit the elongate support assembly to rotate about the longitudinallyaxis.
 44. The surgical system of claim 36, wherein the articulatedsurgical instrument assembly further includes a second end effectorelement coupled to the wrist joint by a second pivotal end effectorjoint so that the first and second end effector elements can manipulatetissues at the worksite therebetween.
 45. The surgical system of claim36, wherein the end effector joints pivot about a common end effectoraxis, and wherein the instrument drive system can move the first andsecond end effector elements independently.
 46. The surgical system ofclaim 36, wherein at least one actuator of the instrument drive systemincludes a rounded drive capstan engaging at least one of the pluralityof elongate drive elements, so as to cause the elongate drive element tomove when the capstan is rotated so as to cause the rotation of at leastone of the plurality of rotary joints of the articulated surgicalinstrument assembly.
 47. The surgical system of claim 46, wherein theelongate drive element comprises a cable element including at least oneportion of cable.
 48. The surgical system of claim 47, wherein the cableelement comprises a continuous loop.
 49. The surgical system of claim36, wherein at least one of the plurality of elongate drive elementsengages an idler pulley, so as to guide the elongate elementintermediate the corresponding actuator and corresponding rotary joint.50. The surgical system of claim 36, wherein at least one of the pivotalwrist joint and the first pivotal end effector joint includes a drivencapstan portion, the driven capstan portion engaging at least one of theplurality of elongate drive elements, so as to cause the pivotal jointto rotate in response to movement of the elongate drive element.